gemstone

Tumbled ruby or ruby-bearing corundum

Corundum (Al₂O₃), red variety colored mainly by chromium

AI-generated identification · may be incorrect

Hardness 9 Mohs; deep pink-red to purplish-red, vitreous luster, nonmetallic, trigonal crystal structure, and no cleavage. The rounded, polished surface indicates tumbling; visible inclusions and uneven color suggest a natural or low-grade specimen.

Identified August 9, 2026More gemstone →

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Physical properties

Formation & geological history

Forms mainly in metamorphic rocks such as marble and amphibolite, or in related igneous deposits, through aluminum-rich, silica-poor conditions. Ruby deposits range from Precambrian to younger geological ages.

Uses & applications

Used as a gemstone when transparent and strongly colored; opaque or fractured pieces are sold as decorative tumbled stones or mineral specimens. Corundum is also used industrially as an abrasive.

Geological facts

Ruby is the red corundum variety; other colors are generally called fancy sapphire. Chromium produces the red color, while inclusions can create distinctive “silk” or asterism.

Field identification & locations

Common sources include Myanmar, Mozambique, Sri Lanka, Thailand, Vietnam, and Madagascar. Confirm identity with hardness testing, refractive-index testing, and gemological examination; visual identification alone cannot distinguish it reliably from garnet or dyed stones.